Polymers, such as polyethylene, have long been used as flexible packaging material. Flexible packages are generally composed of multiple layers that include different types of materials to provide desired functionality, such as flexibility, sealing, barrier, and printing. In food packaging, for example, the flexible packaging material is often used as a protective agent for the food. Flexible packages are also used to house a variety of consumer products, such as products for hair care, beauty care, oral care, health care, personal cleansing, and household cleansing.
Plastic packaging uses nearly 40% of all polymers, a substantial share of which is employed for flexible packaging. Most of the polymers used for flexible packaging applications, such as polyethylene and polyethylene terephthalate, are derived from monomers (e.g., ethylene, terephthalic acid, and ethylene glycol) that are obtained from non-renewable, fossil-based resources (e.g., petroleum, natural gas, and coal). Thus, the price and availability of the petroleum, natural gas, and coal feedstock ultimately have a significant impact on the price of polymers used for flexible packaging materials. As the worldwide price of petroleum, natural gas, and/or coal escalates, so does the price of flexible packaging materials. Furthermore, many consumers display an aversion to purchasing products that are derived from petrochemicals. In some instances, consumers are hesitant to purchase products made from limited non-renewable resources (e.g., petroleum, natural gas and coal). Other consumers may have adverse perceptions about products derived from petrochemicals as being “unnatural” or not environmentally friendly.
In response, producers of flexible packages have begun to use polymers derived from renewable resources (e.g., bio-polyethylene) to produce parts of their packages. These flexible packages, however, still contain a substantial amount of virgin, petroleum-based materials. Some producers have attempted to form flexible packages almost entirely made from polymers derived from renewable resources. For example, Innovia LLC manufactures a metalized cellulose film that contains 90% renewable content, as determined by ASTM 6866-12, that can be made into 12″×2″ sachets (i.e., NatureFlex™). However, when these sachets are filled with water and allowed to sit overnight, visible cracking of the metalized film was observed, and the sachets failed within 24 hours, as evidenced by droplets visibly seeping through the film. Flexible packages composed of polylactic acid (PLA) derived from corn also have met with limited success. Although containers made from PLA are sustainable, industrially compostable, and environmentally friendly, they are currently unfit for long-term preservation because of their sensitivity to heat, shock, and moisture. For example, packages derived from PLA tend to shrivel up, shrink, and break down when exposed to household chemicals, such as bleach and alcohol ethoxylate (i.e., the active ingredient in Mr. Clean®), when the PLA is in direct contact with the product. Frito Lay has produced an all PLA laminate film structure and has disclosed this structure and other variants (e.g., using PLA, PHA, paper, and recycled material) in WO/2009/032748, incorporated herein by reference.
Polyhydroxyalkanoates (PHAs) also have been of general interest for use as renewable materials for forming flexible packaging. For example, U.S. Pat. No. 5,498,692, incorporated herein by reference, discloses a flexible film composed of a polyhydroxyalkanoate copolymer that has at least two randomly repeating monomer units. This film can be used to form, for example, grocery bags, food storage bags, sandwich bags, resealable Ziploc®-type bags, and garbage bags. Flexible packages composed only of PHA, however, will not meet the barrier requirements for most consumer goods. Further, their actual use as a plastic material has been hampered by their thermal instability. PHAs tend to have low melt strengths and may also suffer from a long set time, such that they tend to be difficult to process. Further still, PHAs tend to undergo thermal degradation at very high temperatures. Still further, PHAs have poor gas and moisture barrier properties, and are not well suited for use as packaging materials, as described in US2009/0286090, incorporated herein by reference.
Flexible packages composed of paper that is extrusion coated with a grade of MATER-BI™ thermoplastic starch film manufactured by Novamont are also known. These packages are useful for containing solids, such as, for example, a single serving of sugar, but do not have the barrier properties necessary for many other consumer goods.
Additional materials derived from renewable resources that have been used to form flexible packages include, for example, pectin, gluten, and other proteins. Because these packages are water soluble, they have limited use unless they are contained within exterior packages with moisture barrier properties.
Currently used flexible packaging that is wholly composed of materials derived from renewable resources (e.g., cellulose, PLA, PHA) typically exhibits one or more undesirable properties with respect to manufacture, stability, and performance (e.g., inability to withstand the manufacturing process, short shelf life, and/or poor barrier ability). Accordingly, it would be desirable to provide flexible barrier packaging that is substantially free of virgin, petroleum-based compounds that also includes desirable properties with respect to manufacture, stability, and performance.